If the mkt seriously doubts the long-term creditworthiness of the US as a result of the default (i.e. it's perceived as a more "real", rather than "technical"), TIPS underperform nominals, because TIPS is a more credit-intensive instrument, by construction. If the mkt believes that the disruption has a tangible effect on economic activity (like Leh), TIPS will also underperform the nominals. In both of the cases above, breakeven inflation goes down.
If the mkt seriously thinks that the biggest impact will be felt in the dollar, then TIPS may actually outperform nominals, i.e. breakevens will rally.
Does that answer your question?